How to Set VLC as default even for Mp4 filesīut by default, VLC will not play your MP4 files even after you have manually set VLC as your default media player. Similarly click Music player and set VLC as default.Choose VLC media player from the given list after clicking video player, A window called “Choose an App” will be displayed.On the other side, under Choose default apps, select “Music” given for Music player and “Video” for Video player.Click on Default apps from the left hand side menu of System.Under Settings, click on System (subheading: Display, notifications, apps, power).